Shell and tube type heat exchangers are commonly used in oil refineries, chemical process plants, and other large-scale applications because of their ability to handle high-pressure and high volume fluid flow. Such heat exchangers typically consist of a large pressure vessel or shell and a number of tubes positioned inside the shell. One fluid runs through the tubes, and another fluid runs through the shell and over the tubes to transfer heat from or to the fluid in the tubes.
A non-linear tube heat exchanger is a particular type of shell and tube heat exchanger that includes spiral-turned tubes rather than straight ones. The spiral-turned tubes produce forced vortex fluid motion and/or other fluid agitation and swirl flow to enhance their thermal efficiency and thus permit use of smaller heat exchangers when space is limited.
Heat exchangers with spiral-turned or straight tubes must be tested for defects before they are placed in service and periodically thereafter to ensure optimum performance and to prevent leakage from or into the tubes. This strict separation of fluids can be compromised by tube failure, which may be caused by corrosion, metal erosion, or cracking. Tube failure is additionally problematic because it reduces the thermal efficiency of a heat exchanger and can impede fluid flow. Therefore regular tube inspection and maintenance is desirable. Unfortunately, it is difficult and time-consuming to test shell and tube type heat exchangers, especially those with spiral-turned tubes.